A wireless communication system provides a wireless access service to a user equipment, and includes, to support mobility, transmission points which are referred to as base stations. The base station can provide the wireless access to mobile stations located in a geographical region of a certain range which is referred as a cell.
To provide a service without a spatial gap, the cells can be installed without intervals or to partially overlap each other. Accordingly, a signal transmitted from each cell can exert serious interference on a mobile station which communicates in a neighboring cell. Hence, various techniques for mitigating the interference are studied.
An example of the technique for mitigating the inter-cell interference is coordinated transmission. The coordinated transmission is a control scheme for a plurality of base stations to coordinate mutual signal transmissions to mitigate the inter-cell interference. However, to conduct the coordinated transmission, it is required to rapidly exchange information about resource use of base stations without latency. That is, ideal backhaul connections between the base stations are demanded.
The ideal backhaul can be achieved when hardware of the base stations is physically close or signal paths between the base stations are implemented with a medium which supports rapid communication. However, since an environment including the ideal backhaul cannot be expected for every wireless communication network, the implementation of the coordinated transmission is not guaranteed.